Kinetics and leaching behaviors of aluminum from pharmaceutical blisters in sodium hydroxide solution

A hydrometallurgical process was developed for recycling pharmaceutical blisters.Leaching aluminum from pharmaceutical blisters using sodium hydroxide(NaOH) solutions was investigated with respect to leaching behaviors and kinetics.AL9(34) orthogonal design of experiments suggests that the most significant factor is NaOH concentration followed by temperature and leaching time.Factorial experiments demonstrate that the leaching rate of aluminum increases with increasing of the factors.The optimum conditions are temperature of 70 °C,leaching time of 20 min,NaOH concentration of 1.25 mol/L,liquid-to-solid mass ratio of 15:1 and agitation speed of 400 r/min.Under optimum conditions,the leaching rate is up to 100%,implying that aluminum and polyvinyl chloride(PVC) plastic in pharmaceutical blisters are separated completely.Kinetics of leaching aluminum is best described by the product layer diffusion control model,and the activation energy is calculated to be 19.26 kJ/mol.

Corundum dissolution in concentrated sodium hydroxide solution

The corundum(α-alumina) core has been considered as a suitable candidate for investment casting of hollow, high pressure turbine engine airfoils due to its excellent properties. However, the efficiency of removing alumina cores in concentrated caustic solution cannot meet the needs of industrial production. In this paper, the effects of temperature and initial solution concentration on dissolution of α-alumina were studied by the classical weight-loss method. The fractal kinetic model was developed in order to describe α-alumina dissolution, assuming that the nonporous particles shrank during reaction process. The results show that the dissolution rate increases with increasing reaction temperature and initial solution concentration. Especially, the initial solution concentration has a significant influence on α-alumina dissolution rate at a higher reaction temperature. The activation energies decrease with increasing initial solution concentration, and the chemical reaction is the rate-controlling step.

Preparation of sodium molybdate from molybdenum concentrate by microwave roasting and alkali leaching

The preparation process of sodium molybdate has the disadvantages of high energy consumption,low thermal efficiency,and high raw material requirement of molybdenum trioxide,in order to realize the green and efficient development of molybdenum concentrate resources,this paper proposes a new process for efficient recovery of molybdenum from molybdenum concentrate and preparation of sodium molybdate by microwave-enhanced roasting and alkali leaching.Thermodynamic analysis indicated the feasibility of oxidation roasting of molybdenum concentrate.The effects of roasting temperature,holding time,and power-to-mass ratio on the oxidation product and leaching product sodium molybdate (Na_(2)MoO_(4)·2H_(2)O) were investigated.Under the optimal process conditions:roasting temperature of 700℃,holding time of 110 min,and power-to-mass ratio of 110 W/g,the molybdenum state of existence was converted from MoS_(2) to Mo O3.The process of preparing sodium molybdate by alkali leaching of molybdenum calcine was investigated,the optimal leaching conditions include a solution concentration of 2.5 mol/L,a liquid-to-solid ratio of 2 mL/g,a leaching temperature of 60℃,and leaching solution termination at pH 8.The optimum conditions result in a leaching rate of sodium molybdate of 96.24%.Meanwhile,the content of sodium molybdate reaches 94.08wt%after leaching and removing impurities.Iron and aluminum impurities can be effectively separated by adjusting the pH of the leaching solution with sodium carbonate solution.This research avoids the shortcomings of the traditional process and utilizes the advantages of microwave metallurgy to prepare high-quality sodium molybdate,which provides a new idea for the highvalue utilization of molybdenum concentrate.

Optimization of sodium hydroxide for securing high thermoelectric performance in polycrystalline Sn1−xSe via anisotropy and vacancy synergy

The morphology and composition are two key factors to determine the thermoelectric performance of aqueously synthesized tin selenide(SnSe)crystals;however,their controlling is still under exploring.In this study,we report a high figure-of-merit(ZT)of1.5 at 823 K in p-type polycrystalline Sn1−xSe resulted from a synergy of morphology control and vacancy optimization,realized by carefully tuning the sodium hydroxide(NaOH)concentration during solvothermal synthesis.After a comprehensive investigation on various NaOH concentrations,it was found that an optimized NaOH amount of 10 mL with a concentration of 10 mol L^−1 can simultaneously achieve a large average crystal size and a high Sn vacancy concentration of2.5%.The large microplate-like crystals lead to a considerable anisotropy in the sintered pellets,and the high Sn vacancy level contributes to an optimum hole concentration to the level of2.3×10^19 cm^−3,and in turn a high power factor of7.4μW cm^−1 K^−2 at 823 K,measured along the direction perpendicular to the sintering pressure.In addition,a low thermal conductivity of0.41 W m^−1 K^−1 is achieved by effective phonon scattering at localized crystal imperfections including lattice distortions,grain boundaries,and vacancy domains,as observed by detailed structural characterizations.Furthermore,a competitive compressive strength of52.1 MPa can be achieved along the direction of high thermoelectric performance,indicating a mechanically robust feature.This study provides a new avenue in achieving high thermoelectric performance in SnSe-based thermoelectric materials.

Dimensional Stability Properties of Medium Density Fibreboard (MDF) from Treated Oil Palm (Elaeis guineensis) Empty Fruit Bunches (EFB) Fibres

The aim of the study was to investigate the effect of pre-treatments by using sodium hydroxide (NaOH) and acetic acid on oil palm Empty Fruit Bunch (EFB) fibres for the production of Medium Density Fibreboard (MDF). The EFB fibres were treated with chemicals in the concentration range of 0.2%, 0.4%, 0.6% and 0.8% prior to refining. Single-homogenous layer MDF with 12 mm thickness and density of 720 kg/m3 was produced. Urea-Formaldehyde (UF) was applied at 10% loading (based on dry weight of dry fibres) as a binder. The physical properties (Water Absorption (WA) and Thickness Swelling (TS)) of the produced panels were tested according to European Standard, EN 622-5:2006. The results show that types of chemical used had greater effects than concentration on the dimensional stability of the MDF. EFB fibres treated with acetic acid produced MDF with better dimensional stability compared to the MDF NaOH treated fibres. High concentration of NaOH produced poor dimensional stability in the panels.

Effects of Chemical Treatment on the Physical Properties of Typha

Plant-based concretes are produced from plant aggregates and a binder.Plant fibers are mainly composed of saccharides(sugars)and these sugars can decrease the concentration of Ca2+ions in the cement pore solution and delay the formation of hydration products.To improve the interfacial bond between fibers and matrix a chemical treatment is widely used.This study investigates the effect of sodium hydroxide treatment on physical and hygroscopic properties of Typha aggregates.In particular,a 5%sodium hydroxide solution is used to treat these aggregates and their bulk and absolute densities,porosity,water content and water absorption are evaluated accordingly.Results indicate that bulk and absolute densities increase after treatment from 56.44 kg/m^(3) to 122.57 kg/m^(3) and 541.93 kg/m^(3) to 555.17 kg/m^(3),respectively.NaOH treatment reduces porosity of Typha from 89.58%to 77.92%and decreases water content from 1.4%to 1%.The treatment with sodium hydroxide reduces substantially the water absorption of the aggregates.

Phosphorus Recovery from the Ash of Sewage Sludge Using NaOH by Heat Treatment-II—Reuse of the Alkali Water Generated by Phosphorus Recovery

The phosphorus recovery from the incinerated ash using NaOH by the heat treatment,was investigated.In this method,non-reacted NaOH containing alkali water was generated with the phosphorus recovery.In order to find out the best method for reuse of the alkali water,the alkali water was mixed with new reagent of NaOH,and the phosphorus recovery was carried out.The phosphorus was recovered as a sodium phosphate,and the recovery rate was almost the same even with the reuse of the alkali water.

Determination of Physiochemical Properties of Biosorbents Synthesized from Water Melon Rind Using Microwave Assisted Irradiation Procedure

Three biosorbents were prepared from Watermelon Rind (WMR) using microwave assisted procedure and then characterized using physiochemical techniques (pH, bulk density, volatile matter, surface area, ash content and moisture content). Physiochemical characterization of the synthesized biosorbents was done in order to evaluate their adsorption potentials. Accordingly, results obtained from the experiments conducted revealed the following trend: pH: Water Melon Rind treated with Sodium hydroxide (NaWMR) 8.5 > Water Melon Rind treated with Hydrogen peroxide (HP-WMR) 8.1 > Water Melon Rind treated with Distilled water (DWMR) 6.4 > Untreated Water Melon Rind (UWMR) 5.4, which suggest that NaWMR and HP-WMR possess suitable pH values for the uptake of cationic species within aqueous systems. Surface Area: analysis: UWMR (21.4 m2/g), DWMR (35.8 m2/g), NaWMR (40.6 m2/g) and HP-WMR (61.4 m2/g). This means that HP-WMR has a larger surface area and could be a preferred candidate for adsorption processes. The results obtained from this study suggest that chemical modification of Water Melon Rind (WMR) with either distilled water Sodium Hydroxide or Hydrogen peroxide by means of microwave irradiation enhances physiochemical properties which could boost the adsorption capacity of Water Melon Rind. Thus, the outcome shows that all the three synthesized biosorbents;DWMR, NaWMR and HP-WMR possess the characteristics of a good adsorbent. Accordingly, they can be applied to wastewater treatment process.

ALKALINE PRETREATMENT AND AIR MIXING FOR IMPROVEMENT OF METHANE PRODUCTION FROM ANAEROBIC CO-DIGESTION OF POULTRY LITTER WITH WHEAT STRAW

Alkaline pretreatment(AL)and air mixing(air)both have the potential to improve anaerobic co-digestion(Co-AD)of poultry litter with wheat straw for methane production.In this study,the effects of the combination of AL(pH 12 for 12 h)and air mixing(12 mL·d^(−1))on the Co-AD process were investigated.The substrate hydrolysis was enhanced by AL,with soluble chemical oxygen demand increased by 4.59 times and volatile fatty acids increased by 5.04 times.The cumulative methane yield in the group of Co-AD by AL integrated with air(Co-(AL+air)),being 287 mL·(g VS_(added))^(−1),was improved by 46.7%compared to the control.The cone model was found the best in simulating the methane yield kinetics with R^(2)≥0.9979 and root mean square prediction error(rMSPE)≤3.50.Co-(AL+air)had a larger hydrolysis constant k(0.14 d^(−1))and a shorter lag phaseλ(0.99 d)than the control(k=0.12 d^(−1),λ=2.06 d).The digestate improved the removal of total solids and total volatile solids by 2.0 and 2.3 times,respectively.AL facilitated substrate degradation,while air can enrich the microbial activity,together enhancing the methane generation.The results show that AL+air can be applied as an effective method to improve methane production from the Co-AD process.

Resistance to acid degradation,sorptivity,and setting time of geopolymer mortars

Experimental evaluations were conducted to determine the water sorptivity,setting time,and resistance to a highly acidic environment,of mortar with alkali-activated ground granulated blast furnace slag(GBS)binder and also of combinations of fly ash and GBS binders.Binders were activated using mixtures of NaOH and Na_(2)SiO_(3)solutions.The molarity of NaOH in the mixtures ranged from 10 mol·L^(−1)to 16 mol·L^(−1),and the Na_(2)SiO_(3)/NaOH ratio was varied from 1.5 to 2.5.Mortar samples were produced using three binder combinations:1)GBS as the only binder;2)blended binder with a slag-to-fly ash ratio of 3:1;and 3)mixed binder with 1:1 ratio of slag to fly ash.Mortar samples were mixed and cured at(22±2)°C till the day of the test.The impact of activator solution alkalinity,activator ratio Na_(2)SiO_(3)/NaOH,GBS content on the rate of water absorption were evaluated.After 7,28,and 90 d of immersion in a 10%sulfuric acid solution,the resistance of a geopolymer matrix to degradation was assessed by measuring the change in sample weight.The influence of solution alkalinity and relative fly ash content on setting times was investigated.Alkali-activated mortar with a slag-to-fly ash ratio of 3:1 had the least sorptivity compared to the two other binder combinations,at each curing age,and for mortars made with each of the NaOH alkaline activator concentrations.Mortar sorptivity decreased with age and sodium hydroxide concentrations,suggesting the production of geopolymerization products.No reduction in weight of sample occurred after immersion in the strong acid H_(2)SO_(4)solution for three months,regardless of binder combination.This was due to the synthesis of hydration and geopolymerization products in the presence of curing water,which outweighed the degradation of the geopolymer matrix caused by sulfuric acid.

Thermal defluorination behaviors of PFOS,PFOA and PFBS during regeneration of activated carbon by molten salt

Current study proposes a green regeneration method of activated carbon(AC)laden with Perfluorochemicals(PFCs)from the perspective of environmental safety and resource regeneration.The defluorination efficiencies of AC adsorbed perfluorooctanesulfonate(PFOS),perfluorooctanoic acid(PFOA)and perfluorobutanesulfonate(PFBS)using three molten sodium salts and one molten alkali were compared.Results showed that defluorination efficiencies of molten NaOH for the three PFCs were higher than the other three molten sodium salts at lower temperature.At 700°C,the defluorination efficiencies of PFOS and PFBS using molten NaOH reached to 84.2%and 79.2%,respectively,while the defluorination efficiency of PFOA was 35.3%.In addition,the temperature of molten salt,the holding time and the ratio of salt to carbon were directly proportional to the defluorination efficiency.The low defluorination efficiency of PFOA was due to the low thermal stability of PFOA,which made it difficult to be captured by molten salt.The weight loss range of PFOA was 75°C–125°C,which was much lower than PFOS and PFBS(400°C–500°C).From the perspective of gas production,fluorine-containing gases produced from molten NaOH-treated AC were significantly reduced,which means that environmental risks were significantly reduced.After molten NaOH treatment,the regenerated AC had higher adsorption capacity than that of pre-treated AC.